Over the past five years the Tulane National Primate Research Center (TNPRC) has successfully developed and expanded its specific pathogen free (SPF) rhesus monkey breeding colony. By the end of the current funding period the U24 SPF colony will have grown from a population of zero animals in Year 1 to greater than 1000 animals at the end of Year 5. The colony was completely derived from the TNPRC conventional colony and has matured to the point that production over the next five years will create a self sustaining population allowing assignment of approximately 150 animals per year to NIH funded AIDS research programs. The entire TNPRC SPF colony supported by U24 and U42 grants is the largest in the NCRR/OAR funded program comprising 36 percent of the total animals reflected in the current program census. Over half of the animal allocations from the TNPRC SPF colony over the past five years have been to affiliate (outside) investigators demonstrating our commitment as a national biomedical resource. The further characterization and expansion of the SPF colony proposed in this application will be accomplished using several strategies. Funds have been requested to provide support for the founder SPF breeding stock and their offspring until assignment to AIDS research projects occurs. Funds for viral screening of animals have been requested. The expanded SPF9 (super clean) colony will continue to be grown to meet the needs of specialized AIDS studies including gene therapy, vaccine development and the investigation of opportunistic infections. Because gastrointestinal disease is the leading cause of morbidity and mortality in the TNPRC SPF breeding colonies, we plan to screen animals for selected gastrointestinal agents to further clarify their roles in disease and develop prevention and possible treatment strategies. Behavioral studies will be performed to address specific issues related to the formation of social groups of unrelated animals which has been required to maintain genetic diversity and maintain SPF status. For the colony that is supported by this grant, it is anticipated that 1000 rhesus monkeys will be maintained into the future. The size of the entire TNPRC SPF colony (support from all sources) will be over 3200 animals. Continued support of the TNPRC SPF colony will assist in alleviating the critical national shortage of well characterized rhesus monkeys for the AIDS research effort.